CVE-2018-25235 Overview
CVE-2018-25235 is a buffer overflow vulnerability in NetworkActiv Web Server 4.0. The flaw resides in the username field of the Security options interface. A local attacker can supply an excessively long string through the Set username function to crash the application. The vulnerability is tracked under [CWE-787] for out-of-bounds write conditions. Public exploit code is available via Exploit-DB entry #45302, but no in-the-wild exploitation has been reported. The issue produces a denial of service condition against the web server process.
Critical Impact
A local attacker can crash NetworkActiv Web Server 4.0 by submitting an oversized username value, producing a denial of service on the affected host.
Affected Products
- NetworkActiv Web Server 4.0
- Vendor: NetworkActiv
- CPE: cpe:2.3:a:networkactiv:web_server:*:*:*:*:*:*:*:*
Discovery Timeline
- 2026-03-30 - CVE-2018-25235 published to NVD
- 2026-04-08 - Last updated in NVD database
Technical Details for CVE-2018-25235
Vulnerability Analysis
The vulnerability is an out-of-bounds write [CWE-787] in the username input handler of the Security options panel. NetworkActiv Web Server 4.0 copies user-supplied input into a fixed-size buffer without validating the input length. When an attacker submits a username string longer than the destination buffer, the write operation corrupts adjacent stack or heap memory. The corruption causes the application to terminate, resulting in a denial of service condition against the web server process.
Exploitation requires local access to the system running the management interface. The attacker must reach the Set username function within the Security options. While the public proof of concept targets denial of service, out-of-bounds write conditions can sometimes be escalated to code execution depending on memory layout and compiler protections. The current public advisory documents only crash impact.
Root Cause
The root cause is missing bounds checking on user input within the username configuration routine. The application uses an unsafe string copy without enforcing a maximum length matching the destination buffer size.
Attack Vector
An attacker with local access to the NetworkActiv Web Server administration interface navigates to the Security options, selects Set username, and submits a crafted overlong string. The server process consuming this input writes past the buffer boundary and crashes. No authentication credentials are required beyond access to the local configuration interface. Refer to Exploit-DB #45302 and the VulnCheck Advisory for Network Activ for technical details.
The vulnerability manifests in the username input handler. See the referenced advisory for the specific overflow payload structure used in the public proof of concept.
Detection Methods for CVE-2018-25235
Indicators of Compromise
- Unexpected termination or crash of the NetworkActiv Web Server process on hosts running version 4.0.
- Windows Application or system event log entries referencing an access violation in the web server binary.
- Local user activity opening the Security options configuration interface immediately before a service outage.
Detection Strategies
- Monitor process exit codes and crash dumps associated with the NetworkActiv Web Server executable.
- Alert on repeated restarts of the web server service within short time windows, which can indicate exploitation attempts.
- Inspect local administrative actions against the Security options panel for abnormally long input values.
Monitoring Recommendations
- Forward Windows Error Reporting and application crash telemetry from hosts running NetworkActiv Web Server to a central log repository.
- Track local logon sessions on hosts running the web server to correlate user activity with crash events.
- Establish a baseline for normal restart frequency of the web server service and alert on deviations.
How to Mitigate CVE-2018-25235
Immediate Actions Required
- Restrict local access to systems running NetworkActiv Web Server 4.0 to trusted administrators only.
- Remove or disable the NetworkActiv Web Server 4.0 installation on systems where it is not required.
- Replace NetworkActiv Web Server 4.0 with a supported and actively maintained web server product where feasible.
Patch Information
No vendor patch is currently referenced in the public advisory data for CVE-2018-25235. Consult NetworkActiv Web Server Info and the VulnCheck Advisory for Network Activ for vendor updates. In the absence of a fix, apply compensating controls through access restriction.
Workarounds
- Limit interactive logon rights on hosts running the web server to a minimal set of administrative accounts.
- Apply host firewall rules and operating system access controls to prevent unauthorized users from reaching the management interface.
- Monitor and audit changes to the Security options configuration to identify attempts to set malformed username values.
# Example: restrict local logon to a defined administrators group on Windows
secedit /export /cfg current.cfg
# Edit current.cfg: SeInteractiveLogonRight = *S-1-5-32-544
secedit /configure /db secedit.sdb /cfg current.cfg
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
